EP2582933A1

EP2582933A1 - Method and device pertaining to cooling of dosing units of hc dosing systems for exhaust cleaning

Info

Publication number: EP2582933A1
Application number: EP11798461.7A
Authority: EP
Inventors: Andreas Liljestrand; Per Bremberg; Ulf Carlsson; Lars Eriksson; Erik Gustafsson
Original assignee: Scania CV AB
Current assignee: Scania CV AB
Priority date: 2010-06-21
Filing date: 2011-06-20
Publication date: 2013-04-24
Also published as: BR112012031779A2; SE537643C2; WO2011162691A1; CN102947560A; US20130186068A1; JP2013529747A; SE1050647A1

Abstract

The invention relates to a method pertaining to HC dosing systems for exhaust cleaning which comprise a dosing unit (250) for fuel, comprising the step of deciding about a need, after cessation of an exhaust flow, to cool said fuel dosing unit by means of fuel supplied to it, and the step of predicting a temperature pattern of the dosing unit (250) as a basis for deciding about said need, and predicting accordingly whether a predetermined temperature of the dosing unit (250) will be reached after said cessation of exhaust flow. The invention relates also to a computer programme product containing programme code (P) for a computer (200; 210) for implementing a method according to the invention. The invention relates also to an HC dosing system and a motor vehicle which is equipped with the HC dosing system.

Description

METHOD AND DEVICE PERTAINING TO COOLING OF DOSING UNITS OF HC DOSING SYSTEMS FOR EXHAUST CLEANING

TECHNICAL FIELD

5

The present invention relates to a method pertaining to an HC dosing system for exhaust cleaning which comprises a dosing unit for fuel. The invention relates also to a computer programme product containing programme code for a computer for implementing a method according to the invention. The 10 invention relates also to an HC dosing system for exhaust cleaning which comprises a dosing unit for fuel, and a motor vehicle which is equipped with the HC dosing system.

BACKGROUND

15

In vehicles today, diesel fuel is used as fuel in DPF (diesel particulate filter) systems which comprise a particle filter. The particle filter is adapted to capturing, for example, diesel particles and soot. During active regeneration of the particle filter, diesel fuel is supplied to an exhaust pipe downstream of 20 an engine and is led into an oxidation catalyst, also called DOC. In the oxidation catalyst, said diesel fuel is burnt and causes a rise in the temperature of the exhaust system. Active regeneration of the particle filter situated downstream of the oxidation catalyst can thus be effected.

25 One type of DPF system comprises a container for diesel fuel. The DPF system may also have a pump adapted to drawing said diesel fuel from the container via a suction hose and to supplying it via a pressure hose to a dosing unit situated adjacent to an exhaust system of the vehicle, e.g. adjacent to an exhaust pipe of the exhaust system. The dosing unit is

30 adapted to injecting a necessary amount of diesel fuel into the exhaust pipe upstream of the particle filter according to operating routines stored in a control unit of the vehicle. To make it easier to regulate the pressure when no or only small amounts are being dosed, the system also comprises a return hose which runs back from a pressure side of the system to the container. This configuration makes it possible to cool the dosing unit by means of said diesel fuel which, during cooling, flows from the container via the pump and the dosing unit and back to the container. This results in active cooling of the dosing unit. The return flow from the dosing valve to the container is currently substantially constant. As the dosing unit is currently situated adjacent to the vehicle's exhaust system which becomes warm during operation of the vehicle, e.g. depending on the engine's load, there is risk of the dosing valve becoming overheated. Overheating of the dosing unit may entail degradation of its functionality, potentially impairing its performance.

The dosing unit currently comprises electrical components, certain of them being provided with a circuit card. Said circuit card may for example be adapted to controlling the dosing of diesel fuel to the vehicle's exhaust system. For various reasons, these electrical components are sensitive to high temperatures. Too high temperatures of the dosing unit may result in degradation of the electrical components, potentially leading to expensive repairs at a service workshop. Moreover, diesel fuel present in the dosing unit may at least partly convert to solid form at too high temperatures, potentially leading to obstruction of the dosing unit. According to an example, said diesel fuel undergoes pyrolysis in the dosing unit and is thereby at least partly converted to coke. Thus at least part of said diesel fuel may carbonise. It is therefore of the utmost importance that the temperature of the dosing unit of the DPF system should not exceed a critical level.

Cooling the dosing unit of a vehicle's DPF system is currently effected continuously during the vehicle's ordinary operation as a result of said diesel fuel circulating within the DPF system as indicated above. To some extent, cooling the dosing unit during operation of the vehicle currently works satisfactorily. There is however always a need to improve the performance of vehicles' existing subsystems, e.g. DPF systems, not least from a competition perspective.

During and after operation of the vehicle a large amount of thermal energy caused by its operation is stored in primarily the exhaust system. This thermal energy may be led to the dosing unit from, for example, a silencer and the particle filter and may warm the dosing unit to a temperature which exceeds a critical value.

When the vehicle is switched off and the exhaust flow in the exhaust system consequently ceases, the diesel fuel dosing unit is cooled for a predetermined time, e.g. about 30 minutes, by said diesel fuel in the same way as during ordinary operation.

This arrangement entails certain disadvantages. One is the relatively large amount of energy used to power the pump in the DPF system after the vehicle has been switched off. Any vehicle battery used to power the pump of the DPF system may thus be discharged or reach a relatively low charge level.

Another disadvantage of the dosing unit being cooled in the same way as during ordinary operation is that the pump of the DPF system emits disturbing noise which for example a driver of the vehicle may find irritating, particularly when he/she has to sleep in the cab after a driving run or is in the immediate vicinity of the vehicle. There is thus a need to improve current methods for cooling the dosing unit in the HC dosing system, in order to reduce or eliminate the above disadvantages. SUMMARY OF THE INVENTION

An object of the present invention is to propose a novel and advantageous method for improving the performance of an HC dosing system.

Another object of the present invention is to propose a novel and advantageous HC dosing system and a novel and advantageous computer programme for improving the performance of an HC dosing system.

Another object of the present invention is to propose a novel and advantageous method for effecting cooling of a dosing unit of an HC dosing system after cessation of an exhaust flow therein. Another object of the invention is to propose a novel and advantageous HC dosing system and a novel and advantageous computer programme for effecting cooling of a dosing unit of an HC dosing system after cessation of an exhaust flow therein. A further object is to propose a method, an HC dosing system and a computer programme for reducing the risk that a dosing unit in an HC dosing system might become overheated after cessation of an exhaust flow in the HC dosing system. A further object is to propose an alternative method, an alternative HC dosing system and an alternative computer programme for reducing the risk that a dosing unit in an HC dosing system might become overheated after cessation of an exhaust flow in the HC dosing system. These objects are achieved with a method pertaining to HC dosing systems for exhaust cleaning according to claim 1. An aspect of the invention proposes a method pertaining to HC dosing systems for exhaust cleaning which comprise a dosing unit for fuel, comprising the steps of

- deciding about a need, after cessation of an exhaust flow, to cool said fuel dosing unit, which forms part of the HC dosing system, by means of fuel supplied to the dosing unit, and

- predicting a temperature pattern of the dosing unit as a basis for deciding about said need, and predicting accordingly whether a predetermined temperature of the dosing unit will be reached after said cessation of exhaust flow.

A calculation model adapted to calculating a future maximum temperature which the dosing unit of the HC dosing system, supposing energy stored in the dosing unit, will reach at the cessation of the exhaust flow may be used to achieve a reduced impact of the HC dosing system. A calculation model adapted to calculating a future maximum temperature which the dosing unit, supposing energy stored in further portions of the HC dosing system, will reach at the cessation of the exhaust flow, may be used to achieve a reduced impact of the HC dosing system. The calculation model may be adapted to sampling temperatures of the dosing unit of the HC dosing system just before and/or after cessation of the exhaust flow and be able on the basis thereof to predict whether the dosing unit will reach temperatures which are too high and might damage it. The calculation model may be adapted to sampling temperatures of further portions of the HC dosing system just before and/or after cessation of the exhaust flow and be able on the basis thereof predict whether the dosing unit will reach temperatures which are too high and might damage it. If it is determined that too high a temperature of the fuel dosing unit is very likely to be reached, its cooling by fuel may be maintained at any suitable level. If it is determined that too high a temperature of the fuel dosing unit is very unlikely to be reached, its cooling by fuel may be stopped automatically. Thus the number of occasions which entail continued cooling of the fuel dosing unit by fuel upon cessation of the exhaust flow can be reduced, which is advantageous from several points of view, e.g. in avoiding unnecessary use of electrical energy to run a feed device for said fuel in the HC dosing system. Predicting a temperature pattern of the dosing unit makes it possible for operation of the fuel feed device in the HC dosing system to be controlled in an optimum way with regard to use of electrical energy. Predicting a temperature pattern of the dosing unit and automatically deciding whether continued operation of the feed device should cease makes it possible to avoid unnecessary cooling of the dosing unit.

Said predetermined temperature may be a temperature which is critical for the function of the dosing unit. This functionally critical temperature is a temperature at which, for example, electronic components of the dosing unit might sustain so much damage that their functionality would be degraded or eliminated. Setting said predetermined temperature at a suitable value represents a robust method for reducing any risk of a dosing unit in an HC dosing system becoming overheated after cessation of an exhaust flow in the HC dosing system.

Said further portions of said HC dosing system may comprise any from among a particle filter, e.g. a DPF, a silencer, the dosing unit and the fuel. In particular, it is advantageous to predict a temperature pattern of the dosing unit. If a temperature pattern is predicted for other components of the HC dosing system, e.g. the particle filter or the silencer, it is possible to model on the basis thereof a predicted temperature pattern for the dosing unit. Said prediction of the temperature pattern of said at least one portion of said HC dosing system thus makes it possible to determine indirectly a future temperature of the dosing unit. In particular it makes it possible to determine indirectly a future maximum temperature of the dosing unit. Said prediction of the temperature pattern may entail catering for rewarming effects of at least one portion of the HC dosing system. Depending on how the HC dosing system has been operated, different amounts of thermal energy may be stored in different portions of it. This thermal energy may be led to the dosing unit even after cessation of the exhaust flow. An aspect of the invention caters for rewarming effects when modelling a temperature pattern of the dosing unit.

The method may further comprise the step of predicting said temperature pattern of at least one portion of said HC dosing system by means of a calculation model which comprises a predetermined parameter configuration. The parameter configuration may be any suitable parameter configuration comprising for example a prevailing temperature of the particle filter and/or a prevailing temperature of the silencer and/or a prevailing temperature of the fuel or the dosing unit.

The step of deciding about said need may take place before or after said cessation of exhaust flow. Deciding about said need before cessation of the exhaust flow means that a decision to discontinue cooling the dosing unit may be taken earlier than if the step of so deciding takes place after said cessation of exhaust flow. Deciding about said need after said cessation of the exhaust flow means that a decision to discontinue cooling the dosing unit may be taken on the basis of more updated information than if said need is decided about before cessation of the exhaust flow.

Said fuel may be diesel fuel or some other hydrocarbon-based fuel.

The method is easy to implement in existing motor vehicles. Software pertaining to an HC dosing system for exhaust cleaning according to the invention may be installed in a control unit of the vehicle during the manufacture of the vehicle. A purchaser of the vehicle may thus have the possibility of selecting the function of the method as an option. Alternatively, software which comprises programme code for applying the innovative method pertaining to an HC dosing system for exhaust cleaning may be installed in a control unit of the vehicle on the occasion of upgrading at a service station, in which case the software may be loaded into a memory in the control unit. Implementing the innovative method is therefore cost- effective, particularly since the vehicle need not be provided with any further components or subsystems. Relevant hardware is currently already provided in the vehicle. The invention therefore represents a cost-effective solution to the problems indicated above.

Software comprising programme code for deciding about a need, after cessation of an exhaust flow, to cool a fuel dosing unit, which forms part of the HC dosing system, by means of fuel supplied to the dosing unit, and to predict a temperature pattern of the dosing unit as a basis for deciding about said need, and to predict accordingly whether a predetermined temperature of the dosing unit will be reached after said cessation of exhaust flow, according to an aspect of the invention, is easy to update or replace. Moreover, various parts of the software comprising programme code for applying the innovative method may be replaced independently of one another. This modular configuration is advantageous from a maintenance perspective.

An aspect of the invention proposes an HC dosing system comprising a device for exhaust cleaning which comprises a dosing unit for fuel. The device comprises means for deciding about a need, after cessation of an exhaust flow, to cool said fuel dosing unit, which forms part of the HC dosing system, by means of fuel intended to be supplied to the dosing unit, and means for predicting a temperature pattern of the dosing unit as a basis for deciding about said need, and predicting accordingly whether a predetermined temperature of the dosing unit will be reached after said cessation of exhaust flow. Said predetermined temperature may be a temperature which is critical for the function of the dosing unit.

Said HC dosing system may comprise means for predicting a temperature pattern of the dosing unit and adapted to predicting a temperature pattern of at least one further portion of said HC dosing system comprising any from among a particle filter, a silencer or the fuel.

Said prediction of temperature patterns of said further at least one portion of said HC dosing system may make it possible to determine indirectly a future temperature of the dosing unit.

Said prediction of the temperature pattern may entail catering for rewarming effects of at least one portion of the HC dosing system.

The HC dosing system may further comprise means for predicting said temperature pattern of at least one portion of said HC dosing system by means of a calculation model comprising a predetermined parameter configuration.

The means for deciding about said need may be adapted to so deciding before or after said cessation of exhaust flow.

The above objects are also achieved with a motor vehicle provided with an HC dosing system. The vehicle may be a truck, bus or passenger car.

An advantage of the present invention is that the time when a control unit of the vehicle need not be activated is as often or as long as previously for monitoring and controlling the fuel feed device. An aspect of the invention proposes any suitable platform which comprises an HC dosing system, e.g. a watercraft. The watercraft may be of any kind, e.g. a motorboat, a steamer, a ferry or a ship. An aspect of the invention proposes a computer programme pertaining to HC dosing systems for exhaust cleaning which comprise a dosing unit for fuel, which programme contains programme code stored on a computer-readable medium for causing an electronic control unit or another computer connected to the electronic control unit to perform steps according to any of claims 1-8.

An aspect of the invention proposes a computer programme pertaining to HC dosing systems for exhaust cleaning which comprise a dosing unit for fuel, which programme contains programme code for causing an electronic control unit or another computer connected to the electronic control unit to perform steps according to any of claims 1 -8.

An aspect of the invention proposes a computer programme product containing a programme code stored on a computer-readable medium for performing method steps according to any of claims 1-8 when said programme is run on an electronic control unit or another computer connected to the electronic control unit.

Further objects, advantages and novel features of the present invention will become apparent to one skilled in the art from the following details, and also by putting the invention into practice. Whereas the invention is described below, it should be noted that it is not restricted to the specific details described. Specialists having access to the teachings herein will recognise further applications, modifications and incorporations within other fields, which are within the scope of the invention. BRIEF DESCRIPTION OF THE DRAWINGS

For fuller understanding of the present invention and further objects and advantages of it, the detailed description set out below should be read together with the accompanying drawings, in which the same reference notations denote similar items in the various diagrams, and in which:

Figure 1 illustrates schematically a vehicle according to an embodiment of the invention;

Figure 2 illustrates schematically a subsystem for the vehicle depicted in

Figure 1 , according to an embodiment of the invention;

Figure 3 illustrates schematically a subsystem for the vehicle depicted in

Figure 1 , according to an embodiment of the invention;

Figure 4a is a schematic flowchart of a method according to an embodiment of the invention;

Figure 4b is a more detailed schematic flowchart of a method according to an embodiment of the invention; and

Figure 5 illustrates schematically a computer according to an embodiment of the invention.

DETAILED DESCRIPTION OF THE DRAWINGS

Figure 1 depicts a side view of a vehicle 100. The exemplified vehicle 100 comprises a tractor unit 110 with an engine 150 and a trailer 112. The vehicle may be a heavy vehicle, e.g. a truck or a bus. The vehicle may alternatively be a passenger car.

It should be noted that the invention is applicable to any suitable HC dosing system and is therefore not restricted to DPF systems of motor vehicles. The innovative method and the innovative HC dosing system according to an aspect of the invention are well suited to other platforms which have an HC dosing system than motor vehicles, e.g. watercraft. The watercraft may be of any kind, e.g. motorboats, steamers, ferries or ships.

The innovative method and the innovative HC dosing system according to an aspect of the invention are also well suited to, for example, systems which comprise industrial engines and/or engine-powered industrial robots and/or a stationary engine.

The innovative method and the innovative HC dosing system according to an aspect of the invention are also well suited to various kinds of power plants, e.g. an electric power plant comprising a diesel generator.

The innovative method and the innovative HC dosing system are well suited to any engine system which comprises an engine and an HC dosing system, e.g. on a locomotive or some other platform.

The innovative method and the innovative HC dosing system are well suited to any system which comprises a particle generator (e.g. a combustion engine) and an HC dosing system.

The term "link" refers herein to a communication link which may be a physical connection such as an opto-electronic communication line, or a non-physical connection such as a wireless connection, e.g. a radio link or microwave link. The term "line" refers herein to a passage for holding and conveying a fluid, e.g. a fuel in liquid form. The line may be a pipe of any suitable size. The line may be made of any suitable material, e.g. plastic, rubber or metal.

The term "fuel" refers herein to an agent used for active regeneration of a particle filter of an HC dosing system. Said fuel according to a version is diesel fuel. Other kinds of hydrocarbon-based fuels may of course be used. Diesel fuel is herein cited as an example of a fuel, but one skilled in the art will appreciate that the innovative method and the innovative device are feasible for other types of fuels, subject to necessary adaptations, e.g. adaptations to adequate carbonisation temperatures for fuels adopted, in control algorithms for executing software code in accordance with the innovative method.

Although the term "HC dosing system" is used herein to denote a particle filter system, the invention is not restricted to use of a diesel particle filter. On the contrary, other types of particle filter may be used according to the invention. One skilled in the art will appreciate which kind of fuel is best suited to regenerating the particle filter adopted.

Figure 2 depicts a subsystem 299 of the vehicle 100. The subsystem 299 is situated in the tractor unit 110. The subsystem 299 may form part of an HC dosing system. The subsystem 299 consists according to this example of a container 205 adapted to containing a fuel. The container 205 is adapted to containing a suitable amount of fuel and to being replenishable as necessary. The container may accommodate, for example, 200 or 1500 litres of fuel. A first line 271 is adapted to leading the fuel to a pump 230 from the container 205. The pump 230 may be any suitable pump. The pump 230 may be a diaphragm pump provided with at least one filter. The pump 230 is adapted to being driven by an electric motor. The pump 230 is adapted to drawing the fuel from the container 205 via the first line 271 and supplying it via a second line 272 to a dosing unit 250. The dosing unit 250 comprises an electrically controlled dosing valve by means of which a flow of fuel added to the exhaust system can be controlled. The pump 230 is adapted to pressurising the fuel in the second line 272. The dosing unit 250 is provided with a throttle unit against which said pressure of the fuel is built up in the subsystem 299. The dosing unit 250 is adapted to supplying said fuel to an exhaust system (not depicted) of the vehicle 100. More specifically, the dosing unit 250 is adapted to supplying a suitable amount of fuel in a controlled way to an exhaust system of the vehicle 100. According to this version, a particle filter (not depicted), e.g. a DPF, is situated downstream of a location in the exhaust system where the fuel supply is effected. The amount of fuel supplied in the exhaust system is intended to be used in a conventional way in the HC dosing system for active regeneration of the particle filter. The dosing unit 250 is situated adjacent to, for example, an exhaust pipe which is itself adapted to leading exhaust gases from the combustion engine 150 of the vehicle 100 to said particle filter. The dosing unit 250 is situated in thermal contact with the exhaust system of the vehicle 100. This means that thermal energy stored in, for example, an exhaust pipe, silencer, particle filter and SCR catalyst can thus be led to the dosing unit 250.

The dosing unit 250 is provided with an electronic control card which is adapted to handling communication with a control unit 200. The dosing unit 250 comprises also plastic and/or rubber components which might melt or be otherwise adversely affected as a result of too high temperatures.

The dosing unit 250 is sensitive to temperatures above a certain value, e.g. 120 degrees Celsius. As for example the exhaust pipe, the silencer and the particle filter of the vehicle 100 exceed this temperature value, there is risk that the dosing unit 250 might become overheated during or after operation of the vehicle if not provided with cooling.

A third line 273 runs between the dosing unit 250 and the container 205. The third line 273 is adapted to leading back to the container 205 a certain amount of the fuel fed to the dosing valve 250. This configuration achieves with advantage cooling of the dosing unit 250. The dosing unit 250 is thus cooled by a flow of the fuel when it is pumped through the dosing unit 250 from the pump 230 to the container 205.

A first control unit 200 is arranged for communication with a temperature sensor 220 via a link 293. The temperature sensor 220 is adapted to detecting a prevailing temperature of the fuel where the sensor is fitted. According to this version, the temperature sensor 220 is situated in the container 205. The temperature sensor 220 is adapted to continuously sending signals to the first control unit 200 which contain information about a prevailing temperature of the fuel.

According to an alternative, the temperature sensor 220 is situated adjacent to the dosing unit 250 in order to detect a prevailing temperature there. According to another version, the temperature sensor 220 is situated adjacent to the particle filter of the HC dosing system in order to detect a prevailing temperature there. Any desired number of temperature sensors may be provided in the subsystem 299 to detect a prevailing temperature adjacent thereto. The temperature sensor/sensors 220 is/are adapted to detecting at a suitable location within the subsystem 299 a prevailing temperature which may serve as a basis for controlling operation of the pump 230 in order to cool the dosing unit by means of said flow of fuel.

The first control unit 200 is arranged for communication with the pump 230 via a link 292. The first control unit 200 is adapted to controlling operation of the pump 230 in order for example to regulate a pressure in line 272. In this respect a return flow of the fuel from the dosing unit 250 to the container 205 may be described as a function of a pressure of the fuel upstream of the dosing unit 250. The first control unit 200 is adapted to regulating a prevailing temperature of the dosing unit by controlling operation of the pump 230. The first control unit 200 is arranged for communication with the dosing unit 250 via a link 291. The first control unit 200 is adapted to controlling operation of the dosing unit 250 in order for example to regulate fuel supply to the exhaust system of the vehicle 100. The first control unit 200 is adapted to controlling operation of the dosing unit 250 in order for example to regulate fuel return supply to the container 205.

The first control unit 200 is adapted, according to a version, to using the signals received from the temperature sensor which contain information about a prevailing temperature of the fuel at any suitable location of the HC dosing system as a basis for controlling the pump 230. In particular, the first control unit 200 is adapted, according to a version, to using the signals received which contain a prevailing temperature of the fuel in the region of the temperature sensor 220 as a basis for intermittently controlling operation of the pump 230 at reduced power compared with ordinary operation after cessation of an exhaust flow from the engine.

A second control unit 210 is arranged for communication with the first control unit 200 via a link 290. The second control unit 210 may be detachably connected to the first control unit 200. The second control unit 210 may be a control unit external to the vehicle 100. The second control unit 210 may be adapted to performing the innovative method steps according to the invention. The second control unit 210 may be used to cross-load software to the first control unit 200, particularly software for applying the innovative method. The second control unit 210 may alternatively be arranged for communication with the first control unit 200 via an internal network in the vehicle. The second control unit 210 may be adapted to performing substantially similar functions to those of the first control unit 200, e.g. using the signals received which contain a prevailing temperature of the fuel as a basis for calculating a value for future maximum temperatures of the dosing unit and controlling operation of the pump 230 in any suitable way on the basis of the calculated temperature value. The second control unit 210 may be adapted to deciding about a need, after cessation of an exhaust flow, to cool a fuel dosing unit, which forms part of the HC dosing system, by means of fuel supplied to the dosing unit, and to predicting a temperature pattern of the dosing unit as a basis for deciding about said need, and to predicting accordingly whether a predetermined temperature of the dosing unit will be reached after said cessation of exhaust flow.

It should be noted that the innovative method may be applied by the first control unit 200 and the second control unit 210, or by both the first control unit 200 and the second control unit 210.

According to the embodiment schematically illustrated in Figure 2, the first control unit 200 is adapted to controlling operation of the pump 230 at reduced power compared with ordinary operation, after cessation of an exhaust flow from the engine, in such a way that any amount of electrical energy which may be needed for cooling the dosing unit 250 to at least one critical temperature as regards safety is reduced compared with the state of the art. According to this version, a compressed air source 260 is provided to supply compressed air to the dosing unit 250 via a line 261. The dosing unit 250 is adapted to using said compressed air supply to divide more finely the fuel being dosed. The compressed air may also be used for at least partly causing the dosing unit to dose said fuel into the exhaust duct. The compressed air may also be used to blow out of, for example, the dosing unit 250 any fuel which may be present therein. This may be effected during operation of the engine 150 or after the engine 150 has been switched off.

According to a version, the container 205 may be the vehicle's fuel tank, in which case portions of the vehicle's existing fuel system are utilised according to the present invention. According to another example, the container may be a separate container, i.e. not the same container as the vehicle's fuel tank.

According to a version, the dosing unit 250 is situated immediately adjacent to an exhaust duct of the HC dosing system. According to another example, the dosing unit 250 is provided with a passive nozzle running through said exhaust duct to dose said fuel directly into the exhaust duct.

According to a version, said pump 230 is the same pump as normally generates fuel pressure for an injection system of the engine 150. According to another example, said pump 230 is a separate pump, i.e. not the same pump as normally generates the fuel pressure for the injection system.

According to an example, a precatalyst and/or oxidation catalyst are/is fitted in series with, and upstream of, the particle filter.

Figure 3 illustrates schematically a subsystem 399 of the vehicle 100. The subsystem 399 comprises certain components described above with reference to Figure 2, e.g. the first control unit 200, the second control unit 210 and the temperature sensor 220 for detecting a prevailing temperature of the fuel in the container 205.

The subsystem 399 comprises a temperature sensor 310 adapted to measuring a prevailing temperature of exhaust gases in an exhaust system upstream of the particle filter. The temperature sensor 310 is arranged for communication with the first control unit via the link 311. The temperature sensor 310 is adapted to continuously sending to the first control unit 200 via the link 311 signals which contain information about a prevailing temperature of the exhaust flow. The first control unit 200 is adapted, according to a version, to estimating a prevailing temperature of the particle filter on the basis of the signals received which contain information about a prevailing temperature of the exhaust flow. The subsystem 399 comprises a temperature sensor 320 adapted to measuring a prevailing temperature of the particle filter. The temperature sensor 320 is arranged for communication with the first control unit via a link 321. The temperature sensor 320 is adapted to continuously sending to the first control unit 200 via the link 321 signals which contain information about a prevailing temperature of the particle filter.

The subsystem 399 comprises a temperature sensor 330 adapted to measuring a prevailing temperature of the dosing unit 250. The temperature sensor 330 is arranged for communication with the first control unit via a link 331. The temperature sensor 330 is adapted to continuously sending to the first control unit 200 via the link 331 signals which contain information about a prevailing temperature of the dosing unit 250.

The subsystem 399 comprises a flow sensor 340 adapted to measuring a prevailing flow of the fuel in the HC dosing system. The flow sensor 340 may be situated at any suitable location of the HC dosing system, e.g. adjacent to the line 273 downstream of the dosing unit 250. The flow sensor 340 is arranged for communication with the first control unit via a link 341. The flow sensor 340 is adapted to continuously sending to the first control unit 200 via the link 341 signals which contain information about a prevailing flow of the fuel. The signals sent by the respective sensors 310, 320, 330, 340 and 220 may be used by the first control unit to model a temperature pattern of the dosing unit 250 according to an aspect of the invention. According to a version, the first control unit 200 is adapted to modelling a temperature pattern of the dosing unit 250 on the basis of information in at least one of the signals received from the respective sensors 310, 320, 330, 340 and 220. Figure 4a is a schematic flowchart of a method pertaining to HC dosing systems for exhaust cleaning which comprise a dosing unit for fuel, according to an embodiment of the invention. The method comprises a first step s401. Method step s401 comprises the step of deciding about a need, after cessation of an exhaust flow, to cool said fuel dosing unit, which forms part of the HC dosing system, by means of fuel supplied to the dosing unit, and the step of predicting a temperature pattern of the dosing unit as a basis for deciding about said need, and of predicting accordingly whether a predetermined temperature of the dosing unit will be reached after said cessation of exhaust flow. The method ends after step s401.

Figure 4b is a schematic flowchart of a method pertaining to HC dosing systems for exhaust cleaning which comprise a dosing unit for fuel, according to an embodiment of the invention.

The method comprises a first step s410. Method step s410 comprises the step of shutting off an exhaust flow from a combustion engine of the vehicle 100. At this stage, the dosing unit 250 is cooled in an ordinary way, i.e. at an operating power of the pump 230 which is needed to maintain substantially the same cooling flow for the dosing unit as during ordinary operation. Shutting off the exhaust flow is effected by switching off the engine of the vehicle 100. Step s410 is followed by a step s415.

Method step s415 comprises the step of calculating a future temperature pattern of the dosing unit 250 by means of a calculation model which is stored in the first control unit 200 or the second control unit 210. The calculation of the temperature pattern may be based on one or more of any desired parameters, e.g. a prevailing temperature of the vehicle's particle filter, a prevailing temperature of the fuel, a flow of the fuel in the HC dosing system, a prevailing temperature of the vehicle's silencer, a prevailing temperature of the dosing unit 250, temperatures of an exhaust flow before its cessation and/or a parameter relating to estimated engine load during a certain period before cessation of said exhaust flow. The calculation model is adapted to calculating a prevailing amount of energy stored in various portions of the HC dosing system in order on the basis thereof to calculate and hence predict a temperature pattern of the dosing valve 250 as a basis for deciding about a need to cool the dosing unit 250. Calculating a future temperature pattern of the dosing unit 250 also makes it possible to determine what maximum temperature the dosing unit 250 might reach if cooling does not continue or is discontinued after the cessation of the exhaust flow. Determining a modelled value for a maximum future temperature of the dosing unit 250 makes it possible for operation of the pump 230 to be controlled in an optimum way on the basis thereof. Step s415 is followed by a step s420.

Method step s420 comprises the step of evaluating whether there is a continuing need to cool the dosing unit by means of a flow of the fuel in the HC dosing system. The step of deciding whether there is a need to continue said cooling may be based on the modelled value determined for maximum future temperature of the dosing unit 250. According to an example, deciding whether there is a continuing need for cooling is based on the signals from at least one from among the sensor 220, the sensor 310, the sensor 320, the sensor 330 and the sensor 340, which signals contain information as described above with reference to Figure 3. If there is no continuing need for cooling, the method ends. If there is a continuing need for cooling, a subsequent step s430 is performed.

Method step s430 comprises the step of influencing the operation of the pump 230 in such a way that it is run intermittently and/or at reduced operating power compared with ordinary operation. According to a version, the pump 230 is run intermittently with a predetermined interval configuration. According to a version, the pump 230 is run at an operating power corresponding to ordinary operation. According to a version, the pump 230 is run intermittently at a reduced operating power compared with that employed for maintaining a cooling flow of the dosing unit 250 during ordinary operation. Step s430 is followed by a step s440.

Method step s440 comprises the step of evaluating whether there is a continuing need to continue cooling the dosing unit by means of a flow of the fuel in the HC dosing system. The step of deciding whether there is a need to continue said cooling may be based on an updated modelled value for maximum future temperature of the dosing unit 250. According to a version, the calculation model is adapted to continuously updating a modelled value determined for the future maximum temperature of the dosing unit 250. Calculating an updated value for said maximum temperature may be done in substantially the same way as described, for example, with reference to method step s415. According to an example, deciding whether there is a continuing need for cooling is based on the signals from at least one from among the sensor 220, the sensor 310, the sensor 320, the sensor 330 and the sensor 340, which signals contain information as described above with reference to Figure 3. If it is found that there is no continuing need for cooling, the method ends. If it is found that there is a continuing need for cooling, operation of the pump 230 continues in any way appropriate to ensuring effective cooling of the dosing unit 250. For example, the pump 230 may continue to be run intermittently, possibly also at reduced operating power compared with ordinary operation.

Figure 5 is a diagram of a version of a device 500. The control units 200 and 210 described with reference to Figure 2 may in a version comprise the device 500. The device 500 comprises a non-volatile memory 520, a data processing unit 510 and a read/write memory 550. The non-volatile memory 520 has a first memory element 530 in which a computer programme, e.g. an operating system, is stored for controlling the function of the device 200. The device 500 further comprises a bus controller, a serial communication port, I/O means, an A/D converter, a time and date input and transfer unit, an event counter and an interruption controller (not depicted). The non-volatile memory 520 has also a second memory element 540.

A proposed computer programme P comprises routines for deciding about a need, after cessation of an exhaust flow, to cool a fuel dosing unit, which forms part of the HC dosing system, by means of fuel supplied to the dosing unit, and for predicting a temperature pattern of the dosing unit as a basis for deciding about said need, and for predicting accordingly whether a predetermined temperature of the dosing unit will be reached after said cessation of exhaust flow, according to the innovative method. The programme P comprises routines for predicting whether a predetermined temperature of the dosing unit will be reached after said cessation of exhaust flow. The programme P may be stored in an executable form or in a compressed form in a memory 560 and/or in a read/write memory 550.

Where the data processing unit 510 is described as performing a certain function, it means that the data processing unit 510 effects a certain part of the programme stored in the memory 560, or a certain part of the programme stored in the read/write memory 550.

The data processing device 510 can communicate with a data port 599 via a data bus 515. The non-volatile memory 520 is intended for communication with the data processing unit 510 via a data bus 512. The separate memory 560 is intended to communicate with the data processing unit 510 via a data bus 511. The read/write memory 550 is adapted to communicating with the data processing unit 510 via a data bus 514. The data port 599 may for example have the links 311 , 321 , 331 , 341 , 293 and 290 connected to it (see Figure 3). When data are received on the data port 599, they are temporarily stored in the second memory element 540. When input data received have been temporarily stored, the data processing unit 510 is prepared to effect code execution as described above. According to a version, signals received on the data port 599 contain information about a prevailing temperature of a particle filter of the vehicle 100. According to a version, signals received on the data port 599 contain information about a prevailing temperature of the fuel in the HC dosing system. According to a version, signals received on the data port 599 contain information about a prevailing flow of the fuel, e.g. in the line 273. According to a version, signals received on the data port 599 contain information about a prevailing temperature of the dosing unit 250 of the HC dosing system. According to a version, signals received on the data port 599 contain information about a prevailing temperature of an exhaust flow in the exhaust system of the vehicle 100.

The signals received on the data port 599 may be used by the device 500 to decide by means of a calculation model stored in the device 500 about a need, after cessation of an exhaust flow, to cool a fuel dosing unit, which forms part of the HC dosing system, by means of fuel supplied to the dosing unit, and to predict a temperature pattern of the dosing unit as a basis for deciding about said need, and predict accordingly whether a predetermined temperature of the dosing unit will be reached after said cessation of exhaust flow.

Parts of the methods herein described may be effected by the device 500 by means of the data processing unit 510 which runs the programme stored in the memory 560 or the read/write memory 550. When the device 500 runs the programme, methods herein described are executed.

The foregoing description of the preferred embodiments of the present invention is provided for illustrative and descriptive purposes. It is not intended to be exhaustive or to restrict the invention to the variants described. Many modifications and variants will obviously be apparent to one skilled in the art. The embodiments have been chosen and described in order best to explain the principles of the invention and its practical applications and hence make it possible for specialists to understand the invention for various embodiments and with the various modifications appropriate to the intended use.

Claims

1. A method pertaining to HC dosing systems for exhaust cleaning which comprise a dosing unit (250) for fuel, comprising the step of

- deciding about a need, before cessation of an exhaust flow, to cool said fuel dosing unit (250) by means of fuel supplied to it,

characterised by the steps of

- predicting a temperature pattern of the dosing unit (250) as a basis for deciding about said need, and accordingly

- predicting whether a predetermined temperature of the dosing unit (250) will be reached after said cessation of exhaust flow.

2. The method according to claim 1 , whereby said predetermined temperature is a functionally critical temperature for the dosing unit (250).

3. A method according to any one of the foregoing claims, whereby a temperature pattern of at least one further portion of said HC dosing system comprising any from among a particle filter, a silencer and the fuel is predicted.

4. A method according to claim 3, whereby said prediction of temperature pattern of said at least one portion of said HC dosing system is used for indirect determination of a future temperature of the dosing unit (250).

5. A method according to any one of the foregoing claims, whereby said prediction of the temperature pattern entails catering for rewarming effects of at least one portion of the HC dosing system.

6. A method according to any one of the foregoing claims, further comprising the step of - predicting said temperature pattern of at least one portion of said HC dosing system by means of a calculation model comprising a predetermined parameter configuration.

7. A method according to claim 6, whereby the step of deciding about said need takes place before said cessation of exhaust flow or after said cessation of exhaust flow.

8. A method according to any one of the foregoing claims, whereby said fuel is diesel fuel or some other hydrocarbon-based fuel.

9. An HC dosing system comprising a device for exhaust cleaning which comprises a dosing unit (250) for fuel, comprising

- means (200; 210; 500) for deciding about a need, after cessation of an exhaust flow, to cool said fuel dosing unit (250) by means of fuel intended to be supplied to it,

characterised by

- means (200; 210; 500) for predicting a temperature pattern of said dosing unit (250) as a basis for deciding about said need, and accordingly

- means (200; 210; 500) for predicting whether a predetermined temperature of the dosing unit (250) will be reached after said cessation of exhaust flow.

10. An HC dosing system according to claim 9, in which said predetermined temperature is a functionally critical temperature for the dosing unit (250).

11. An HC dosing system according to either of claims 9 and 10, in which said means (200; 210; 500) for predicting a temperature pattern of the dosing unit are adapted to predicting a temperature pattern of at least one further portion of said HC dosing system comprising any from among a particle filter, a silencer and the fuel.

12. An HC dosing system according to any one of claims 9-11 , in which said prediction of temperature pattern of said at least one portion of said HC dosing system makes it possible to determine indirectly a future temperature of the dosing unit (250).

13. An HC dosing system according to any one of claims 9-12, in which said prediction of the temperature pattern entails catering for rewarming effects of at least one portion of the HC dosing system.

14. An HC dosing system according to any one of claims 9-13, further comprising

- means (200; 210; 500) for predicting said temperature pattern of at least one portion of said HC dosing system by means of a calculation model comprising a predetermined parameter configuration.

15. An HC dosing system according to claim 14, in which the means for deciding about said need are adapted to so deciding before said cessation of exhaust flow, or in which the means for deciding about said need are adapted to so deciding after said cessation of exhaust flow.

16. A device according to any one of claims 9-15, in which said fuel is diesel fuel or some other hydrocarbon-based fuel.

17. A motor vehicle (100; 110) comprising an HC dosing system according to any one of claims 9-16.

18. A motor vehicle (100; 110) according to claim 17, which vehicle is any from among truck, bus or passenger car.

19. A computer programme (P) pertaining to HC dosing systems for exhaust cleaning which comprise a dosing unit (250) for fuel, which programme (P) contains programme code for causing an electronic control unit (200; 500) or another computer (210; 500) connected to the electronic control unit (200; 500) to perform steps according to any of claims 1-8.

20. A computer programme product containing a programme code stored on a computer-readable medium for performing method steps according to any of claims 1-8 when said computer programme is run on an electronic control unit (200; 500) or another computer (210; 500) connected to the electronic control unit (200; 500).